1. Field of Invention
This invention relates to a composition for the decoration and/or coloration of polyolefin surfaces and to a method for its preparation.
2. Brief Statement of the Prior Art
Polyolefin surfaces and, in particular, polyethylene surfaces are very non-receptive to coatings such as paints, inks and the like. Consequently, it is very difficult to impart a permanent indicia, either decoration or printed matter, on the surface of a polyolefin object. Various techniques have been attempted such as flame treatment to condition or partially oxidize the surface of the polyolefin object to render it receptive to a pigmented coating materials such as inks or paints.
In U.S. Pat. Nos. 4,252,762 and 4,519,972, methods are disclosed for imprinting or decorating the surface of rotationally molded products. The methods comprise coating the interior surfaces of the rotational mold with a suspension of a pigment in an oil or wax, followed by an otherwise conventional rotational molding operation. While these patented methods achieve a permanent bonding of paints or inks to a polyolefin object, it is frequently desirable to apply graphics or printing to polyolefin objects after their formation.
In our prior patent U.S. Pat. No. 5,746,961, we disclose a coating composition of particles of polyethylene and a surface enhancing solid such as Teflon suspended in an organic or aqueous liquid carrier and the method of its use to enhance the surfaces of molded plastic parts. In our application, U.S. Ser. No. 08/914,536, we disclose and claim a related coating composition of particles of polyethylene and a colorant (pigment) suspended in an organic liquid carrier and a method of its use to color the surfaces of molded polyolefin articles. These compositions are applied as a film onto the surfaces of polyethylene objects and are permanently incorporated into the polyethylene surfaces by mild heating. Critical to the functioning of these coatings is the presence of a binding component to retain the coating film on the polyethylene surfaces prior to the heating step.
Environmental concerns have disfavored use of coating compositions with organic carriers or solvents, and it desirable to provide colorant coating compositirly all liquids, particularly aqueous liquids, imposing obstacles to the use of aqueous base coating compositions and to the preparation of a stable dispersion of polyethylene particles in the water carrier.
It is an objective of this invention to provide an aqueous-base composition for the coloration of the surface of a polyolefin object.
It is a further objective of the invention to provide a method for the preparation of a stable aqueous-base coating composition containing components of particulate polyethylene, colorant and binder.
It is likewise an objective of this invention to provide an aqueous-base coating composition containing particulate polyethylene with a binder that is effective in retaining an applied film of the coating composition after its application to the surface of a polyolefin object and prior to the thermal bonding of the composition into the polyethylene surface.
Other and related objectives will be apparent from the following description of the invention.